1. Field of the Art
This invention relates to a semiconductor device and a manufacturing method thereof.
2. Description of the Related Art
In recent years, the research of semiconductor devices has been increasingly conducted by use of the very chemically stable nature of silicon carbide (SiC). Silicon carbide has a larger energy gap Eg, as compared with silicon, for example, Eg=3.3 eV in the case of 4H type crystals, to have a high withstanding voltage and therefore expected to be applied to power devices such as an electric power controlling device.
An exemplary SiC bipolar transistor comprises a high-concentration n+-type SiC substrate on which are laminated the n−-type epitaxial region, a p-type base region, and the p+-type contact region in this order. The topmost p+-type contact region is partially removed to expose part of the p-type base region located thereunder. An n+-type emitter region is formed in the surface layer of the p-type base region as exposed. An interlayer film is formed on the surface of the n+-type emitter region and the surface of the p+-type contact region serves to protect and stabilize the surfaces and the junction surfaces thereof while an emitter electrode and a base electrode is formed through contact holes opened through the interlayer film. Also, an collector electrode is formed on the rare surface of the SiC substrate.
In operation of this vertical bipolar transistor having a high withstanding voltage for high power applications, a larger collector current can be generated from the collector electrode to the emitter electrode in response to a smaller base current passed from the base electrode to the emitter electrode. Features reside in that a large quantity of carriers are injected to an n−-type epitaxial layer having a high specific resistance to cause conductivity modulation and decrease the “on” resistance of the semiconductor device. If no voltage is applied to the base electrode, no base current flows to electrically insulate between the collector electrode and the emitter electrode and realize a switching operation.